Nice article, but the Allagash has changed. When I first traveled it in the 1960's, the water was freezing, the water levels were steady and the fishing was great. Heavy cutting near the Allagash (leaving only a beauty strip on either side of the river) changed the climate remarkably. With no forest, the rains would run off quickly (leading to quick rises and drops in the water level), the water was warm and the trout and salmon left for cooler waters. It is also far more accessible now than then, although that does not appear to have dawned on many people.
The St. John (a much wilder river) always had its passable and impassable weeks, but the Allagash was old faithful, always having great water. Now, you need to check the weather and stream gauges on each before you go (or bring some wheels for your canoe).
However, there is still no other place I would prefer to be on midsummer's night's eve.